MUSEUM OF COMPARATIVE ZOOLOGY. 259 



plates, with large genital and ocular plates, which, however, are not bare 

 as in that genus, but carry small, rudimentary, knob-shaped spines. The 

 genital openings are near the anal system. The buccal membrane carries 

 ten large quadrangular plates, with rounded edges placed near the test, the 

 whole space between them and the mouth being covered by small plates ; 

 the rest of the membrane is bare. The actinal opening is large, the cuts 

 slight, and the pores are not arranged in ares near the mouth as in Echino- 

 cidaris. The spines are sharp, (hit spindle-shaped, with a prominent ridge 

 running along the middle of the upper surface, the section is triang- 

 ular, the longest side being the under side, which is convex, the shorter 

 upper sides being concave. The spines are finely granulated longitudinally 

 with a slightly serrate edge. The large spines, as well as the knobs of the 

 rudimentary spines, are sometimes beautifully colored by dark violet pig- 

 ment cells, following the arrangement of the granulation. The pedicellaria; 

 have the same coloration. The tentacles, to judge from alcoholic specimens, 

 must have been very large, though not possessed of a powerful disk ; the 

 test, when prepared to show the structure, was of a delicate cream color, 

 upon which the brilliant coloration of the knob-shaped spines stood out in 

 bold relief. 



From 138 to 315 fathoms. 



Eehinometra Michelini Des., Agass. Cat. Rais. 



Syn. Eehinometra Michelini A. Ag. (non. Lutk.) Bull. Mus. C. Z., No. 2. 

 Eehinometra lucunter Lutic, Bid. (non. Lam.) 



" lobata Blaix., Article Oursin. 



Helioridaris mexicana Auct. (non. Ag.) 

 Heliocidaris CastidnauJi IIupe in Casteln. 



From an examination of typical specimens of Eehinometra lucunter 

 Lam. it became evident that Lamarck's species was the common Eehinome- 

 tra, having such an extensive range in the Pacific and Indian Oceans ; 

 extending from the Sandwich Islands to the Red Sea. It is with some 

 doubt, however, that the above name has been adopted for our common 

 "West India species, the varieties of which have served as the type of 

 many species ; the large, somewhat oblong, swollen-sided adult, with short 

 stout spines, has been the Eehinometra lobata Blaix., the flatter, more 

 circular variety, with long slender spines, has even been referred to a differ- 

 ent genus Heliocidaris by Ilupe. Authors generally have referred the 

 young flat stage to Heliocidaris mexicana Ag. It is somewhat remarkable 

 that with the extensive geographical distribution of this species (the 

 whole coast of Brazil, the Gulf of Mexico, Caribbean Sea, West India 

 Islands, Bahamas, and Bermudas) it should be so limited in bathymetri- 

 cal range. 



Littoral, to G to 7 fathoms. 



